In a power generator such as a wind power generator or a solar power generator using natural energy, since the output is highly influenced by weather conditions, it is difficult to generate power according to demand. In addition, because system voltages or frequencies vary depending on output fluctuations, the level of deployment is limited due to system operating restrictions.
In order to overcome these problems, recently, as described in Publication of Japanese Patent No. 3352662 (Patent Document 1) and so forth, there has been progress in the development of a hybrid-type distributed power supply system that realizes high-quality and stable power supply by combining a power generator using natural energy with an electrical power storage device such as a secondary battery, and by controlling the output fluctuation of the power generator using the electrical power storage device.    Patent Document 1: Publication of Japanese Patent No. 3352662 (pages 2-7, FIG. 1)